EP1214488B1

EP1214488B1 - Two stage attachment means for lid and base container of stands for tetherball games

Info

Publication number: EP1214488B1
Application number: EP00912229A
Authority: EP
Inventors: Ian Gavin Gormley
Original assignee: European Sports Merchandising BV
Current assignee: European Sports Merchandising BV
Priority date: 1999-09-10
Filing date: 2000-01-19
Publication date: 2004-09-22
Anticipated expiration: 2020-01-19
Also published as: WO2001018328A1; US6565459B2; GB0001566D0; GB2354018B; AU3398900A; DE60014121T2; EP1214488A1; DE60014121D1; US6328665B1; AU777179B2; GB2354018A; US20020028716A1

Description

TECHNICAL FIELD OF THE INVENTION

This invention relates to movable stands for vertical pole support comprising a base container and a detachable lid. which may be filled with ballast material. in particular, but not necessarily, for stressful applications such as for games having a vertical pole of the tether-ball type, such as the tether tennis game known as "SWINGBALL" (Trade Mark) or the tethered soccer-ball game known as "SOCCER SWINGBALL" (Trade Mark), where the pole held by the stand may be subjected to violent shocks and pressures during the playing of such games. The stand may also conveniently be used for other sporting activities such as basketball. or other applications such as for holding umbrella poles.

In describing a stand as movable, this refers to the feature that such stands arc not normally immovably fixed or positively anchored to the ground. When not filled with ballast. the stand is light and easily transportable. When filled with ballast. while providing stable support for a pole, it will still be practical to move the base from one location to another.

Tether tennis type games, such as "SWINGBALL" (Trade Mark), include a pole which traditionally has been anchored by forcing the lower end vertically directly into the ground, which is facilitated by a pointed lower end of the pole. The pole has a helical anchoring device at its upper end and a tennis type ball is tethered to this by a cord.

The game is played by the striking of the ball with racquets or paddles by opponents in opposite directions around the pole, causing the attachment of the line to the helix to rise up or down the helix.

The tethered soccer-ball game "SOCCER SWINGBALL" (Trade Mark), is similar to SWINGBALL (Trade Mark). except that the ball is substantially larger and heavier, of the football or soccer ball type, and the pole is shorter. so that the football may be kicked around the pole at ground level.

it will be appreciated that considerable stress can be transferred to the pole during play of games of this type and if the pole is anchored in soft ground. it has been found that the pole soon becomes loose. It will also be appreciated that it will not be possible to play games of this type where the pole is unable to be inserted into hard soil, or where the game is required to be played on any other type of hard surface which the pole end cannot penetrate.

Games of the tether tennis type have been marketed for many years and an on-going search has been mounted for a suitable stand to enable such games to be played on hard surfaces. where it is not possible to force the point of the pole into the ground. or where the ground is too soft to hold the pole firmly upright during play.

One of the main problems is that a suitable stand for games of this type has to be extremely robust to withstand the pressures and shocks which have to be absorbed by the stand during play.

BACKGROUND ART

One type of stand which has been tried for use with tetherball type games is the blow-moulded plastic beach umbrella stand. Typically these weigh about 1 to 2 kilograms (2 to 4 pounds) when empty, are blow-moulded in high density polyethylene plastic and have a filler hole on the top through which water. as ballast material, can be poured in, or out.

These stands normally have a capacity of about 15 to 25 litres (0.5 to 1 cubic feet), cover a surface area of about 0.5 x 0.5 metres (1.5 x 1.5 feet) and weigh about 15 to 25 kilograms (30 to 50 pounds) when filled with water as ballast material and are fitted with a central internal socket and clamping means to receive and hold the bottom end of a beach umbrella pole therein.

One of the problems with the use of blow-moulded stands of this type for tetherball games. is that the blow-moulding process distributes a layer of plastic material of uniform thickness over the surface of the mould, resulting in a reasonably uniform wall thickness of the stand. This makes it difficult to provide for localized thickened sections. so as to reinforce areas subject to particularly high stresses during play, such as the socket and the area adjacent. which holds the bottom end of the pole, or the area of the upper surface adjacent to the pole. After extended play stands of this type tend to rupture or split in these areas and are therefore unsuitable for use with tetherball games.

Blow-moulded stands are also bulky to store and transport, and while ballast material such as water may be added or removed through a filler hole, it is more laborious with sand or gravel. and, depending on the size of the filler hole (which may not be so big so as to compromise the structural integrity of the stand) virtually impossible to use large objects such as bricks or stones as ballast material.

An attempt to obviate the problem of bulkiness of stands for garden umbrellas has been made in U S Patent 4 591 126 (Sheldon Bemey), which provides for a base or stand having a base section and a separate lid portion.

This lid is designed to inter-connect to the base by a peripheral continuous snap sealing means of the tongue and groove type. However, no reference is made to any need to remove the lid from the base having been assembled, and in particular, no reference is made to the ease of removing the lid in terms of the pressure required to unlock the snap fit. This invention does not refer to the requirements of stressful applications, such as games of the tether tennis type, that the lid remain attached to the base during play. and also be easily detachable by young children. or that the seal between lid and base be effective for the containment of ballast material during such use.

A different type of stand, which did attempt to address the requirements of tetherball games. is described in US Patent No. 4148455. The stand in this patent comprises a base container for water or sand or other ballast, and has a formation for receiving the bottom end of the pole.

The removable lid has an orifice with formations, which co-act with a foot plate on the pole. so as to prevent rotation of the pole. There is however, no detailed reference or description of the peripheral sealing arrangement between lid and base in this patent. The problem with the design of this stand is that the lid is described as being "easily snapped in and out of place" (lines 42 and 43 of column two of US Patent No. 414 8455).

There is no positive locking arrangement for the lid and base container apart from this "snap" action and under the pressure of shocks exerted in stressful applications such as the playing of tether ball games. the snap seal between the lid and the base can break loose allowing water ballast to spill freely out of the base container or even for the lid to become completely unseated from the base container. Because of this design defect. the stand is unsuitable for stressful applications such as tether ball type games and a stand according to US Patent No. 414 8455 as far as is known has never been made available commercially.

As a general comment, as well as in referring to the above US Patent 4 591 126 and US Patent 4 148 455. it should perhaps be noted that when assessing the suitability of the design of stands for poles for use in stressful applications which have removable lids. and where such lids are designed to engage the base container with a "snap" fit, that snap sealing means of this type face the contradictory requirements of providing a strong attachment of the lid to the base, together with a contrasting need in applications such as envisaged in this patent application, for the joint to be easily releasable by young children.

US Patent 4 712 328 (GIES) also describes a stand.

This has a base casing 1, and a rotatable cover 12, which, when rotated, actuates internal clamping cylinders 4A, 4B and 4C to grip the bottom end of the trunk of a tree. There is no provision for rotational motion of the lid in relation to the base, or any similar clamping mechanism, in the present invention.

With regard to the sealing arrangement between cover and base, GIES has no continuous seal around the periphery of the joint between cover and base, as the guide pins 11, which protrude into the guide slots 10, are designed to slide along the guide slots 10, when the cover 12, is rotated.

The guide pins 11 do not fill the guide slots 10 longitudinally along their complete length, if they did, it would not be possible to rotate the cover. The guide pins therefore do not provide a total peripheral seal as is done with the tongue and groove arrangement of the present invention.

With regard to the clamping arrangements between cover and base, there is only a single attachment point by means of the clamping pins. A single attachment point will not provide the required degree of attachment which is needed when the pole is subjected to the shocks and stresses incurred in the playing of tether ball games.

Finally, there is no reference to the use of ballast material, which is need to provide the stability required for tether ball games. It is probable that the insertion of ballast into the "GIES" stand would interfere with the sophisticated clamping mechanism.

In addition, the guide slots (1o) of GIES are open on both sides of the casing and pierce the casing from one side to the other. The are not analogous to the groove of the present invention, as a groove by definition, is open only on one side. The GIES slot/pin arrangement is fundamentally of different design and will not afford the same degree of integrity of the seal between cover and base as is provided by the tongue and groove arrangement of the present invention.

In general therefore, a lid which engages with a releasable snap fit to a base container is not suitable for the applications envisaged by this patent application.

It is an object of this present invention to provide a robust movable stand for vertical pole support having a rigid. or semi-rigid, base container component and an easily detachable lid component. which will hold a pole in its mounted position, particularly for use in conjunction with stressful applications such as for games of the tether ball type, which will resist the violent jerks encountered during the play of these games. without the lid becoming free of the base container, and which will a.lso maintain an effective seal between the lid and base container. so as to prevent the escape of water or other types of ballast through this joint during play.

It will be appreciated that this stand may also conveniently be used as apparatus for other sporting activities such as basketball, or for holding umbrella poles, or other applications, even though the shocks and pressures in these applications may net be as onerous as for games of the tetherball type.

DISCLOSURE OF THE INVENTION

According to the present invention. a movable stand is provided for vertical pole support in which the lid and base container components are attached together by a two stage attachment system which. in combination. provide an effective attachment between the lid and base container for use in stressful applications such as for games of the tetherball type as described previously.

The lid and container are rigid or semi-rigid, and preferably moulded from plastic materials. In addition. locking or clamping means may be provided to positively secure any pole which is mounted in the stand, so that the pole is unable to pull free from its mounted position in the stand, unless such locking means are released.

The primary attachment means between the lid and the base components consists of a complemental inter-engageable tongue and groove formation, in which the tongue member, of little width compared with its height in cross section, located around the periphery of the one component, fits into and is there enveloped and held closely by the groove at the periphery of the other component.

This primary attachment means implements an effective seal between the lid and base container which prevents water or other ballast from leaking out through the joint. should the base container be shaken or jolted, as can occur during play of games of the tetherball type.

An important aspect of this tongue and groove design is that at all points of this joint around the peripheries of the base container and lid, the tongue is held on both sides by the groove so as to resist at any point displacement of the lid relative to the base by shocks or jolts from either side which might be imparted during play of games of the tetherball type.

In a preferred form of the invention, the mating of the tongue and groove joint of the primary attachment system is achieved by the provision of a tongue which usually comprises the peripheral rim of the base container which has to be forced into a complimentary flexible groove, which is provided at the periphery of the lid of the stand, which flexes open or moves in relation to the tongue, so at to accommodate the insertion of the tongue, such flexibility being imparted by its design, and by the inherent characteristics of the material used in the manufacture of the groove which is preferably plastic.

The fit of the tongue to the groove is such that either on initial presentation of the tongue to the opening of the groove. or during insertion of the tongue into the groove, the tongue is either larger than the groove. or the tongue and groove are vertically non-aligned with the base container which includes the position where the tongue and groove are at an obtuse angle 51 to the axis of the base container 50 (See FIG. 4C).

The tongue may therefore not be fully inserted into the groove unless, by the application of pressure, the flexible groove is forced open, or moved into alignment, or forced over the obtuse angle of the leading edge of the tongue. Having opened or aligned the groove. the tongue is inserted to the maximum extent into the groove, in which position the tongue is enveloped and held closely by the groove.

The groove is so configured that, having been forced open to accommodate the full insertion of the tongue to the maximum extent, it is able, by virtue of its inherent flexibility and springiness. to spring or snap back substantially to its normal configuration when not under stress, while enveloping the tongue. This spring action and bias of the groove towards its natural disposition when not under stress, positively restrains the enveloped tongue inside the groove in the fully closed position, where the tongue is inserted to the maximum extent, unless sufficient force is exerted on the flexible groove so as to cause it to open to allow the release of the tongue.

While the tongue is of little width in relation to its height in cross section, the tongue may also possibly be hollow in cross section.

Although this primary attachment means provides an effective watertight seal, it is also designed for easy engagement or disengagement, and is characterized in that relatively light finger pressure of no more than about 10 kilograms (20 pounds) or preferably of the order of no more than about 3 kilograms (5 pounds) is required to press the tongue into the groove to the fully ciosed position.

In this regard finger pressure means the application of one or more fingers having a total area of the fingers exerting pressure over about 0.5 to 10cm² (0.1 to 1 square inches) and preferably between 2 to 5cm² (0.25 and 0.75 square inches).

Conversely, the application of finger pressure of not more than about 10 kilograms (20 pounds) or preferably of the order of no more than about 3 kilograms (5 pounds) is required to pull the tongue free from the groove of the primary attachment means.

With regard to these limits on the forces required to engage or disengage the tongue and groove seal of the primary attachment means, it has been found that these are the maximum reasonable pressures which can be reasonably expected to be exerted by children, should they wish to easily and quickly assemble or disassemble the lid and base container components.

A major feature of tongue and groove sealing designs of this type is that they are designed not only to join the lid and base snugly together in the closed position, but also to allow the easy attachment or separation of the lid and base, which facilitates the convenience of frequent use of the stand.

The problem that emerged during development and testing is that pressure and shock-loads considerably greater than about 10 kilograms (20 pounds) can be exerted on the joint between lid and base in stressful applications such as during the playing of tetherball games. which a joint of this type alone. conforming to this limit for engagement or disengagement purposes. is sometimes unable to contain. resulting in breaking of the seal. and the lid pulling loose from the base, so that play is no longer possible.

Stronger, heavy duty tongue and groove designs for attachment of lids to base containers are available which would resist such higher pressures during play, bu: which also require much greater attachment, or detachment, pressures. These are necessitated for example, in the sealing arrangements of plastic paint containers which obviously must not come undone even if dropped when full of paint.

The much higher attachment or detachment pressures required for the use of these heavy duty tongue and groove designs necessitate the application of considerable force and possibly, the use of tools or levers, which is unacceptable for domestic use, and particularly for children. It was therefore decided to provide additional, separate, secondary attachment means of a different nature, requiring little pressure and easy to engage, which would enable the primary seal to be maintained even if pressures or shock loads considerably higher than about 10 kilograms (20 pounds) are experienced.

A secondary attachment system is therefore also provided, which consists of the provision of two or more locking devices at points around the periphery of the base container. These locking devices are capable of attachment and detachment by the application of finger pressure of no more than about 10 kilograms (20 pounds) and preferably of the order of no more than about 0.5 kilograms (1 pound).

The locking devices positively lock the lid to the base container and prevent the extraction of the tongue from the groove of the primary attachment stage, or the detachment of the lid from the base container, except by the application of excessive force, having regard to the conventional use of the stand.

In view of the shocks and stresses generated in stressful applications such as during the playing of tether tennis type games and the resulting premature breakage problems experienced in this respect particularly while using stands of the blow moulded umbrella stand type, an extensive testing programme was undertaken with a stand according to this patent application, which was tested by the playing of a tether tennis type same. This included specific attention to the strength of the two stage attachment system, with particular reference to the tongue and groove primary attachment system which is of relatively light duty construction, so as to permit easy engagement or disengagement.

Tests were carried out with adult players, to the extent of hitting over 205,000 full blows of a rigid faced bat on the tennis ball, which was followed by a further 32.000 blows with a full size, full weight, strung tennis racket. To some surprise, no serious flaws whatsoever became evident during this test programme.

At this point it was decided that the test programme thus far was more than adequate proof of the integrity of the stand, and as all concerned were exhausted. the test was terminated. It should be noted however, that the stand was still in very good condition, and it was probable that testing could have continued for even longer without risk of any breakage or failure.

As a result of this test programme it was conclusively established that a stand according to this patent application is able to withstand the severe conditions imposed when using the stand with games of the tether tennis type. In this regard it should be noted that it was discovered during the test programme that extensive long term testing is essential, as designs which after substantial initial testing appeared appropriate, subsequently failed during on-going further testing.

An additional option for the stand is the provision of clamping means associated with the lid, in the area of the hole in the lid through which the pole is inserted when mounting the pole in the stand, which positively secures the pole in its mounted position, so that it is unable to pull free unless the clamping means are released (as illustrated in FIG. 6).

A further feature may be provided by way of a vertical socket, or hollow tube, on the floor of the base container positioned under the hole in the lid for the pole. This socket may be provided with clamping means for the pole. and serves to isolate the end of the pole from the ballast material in the base container.

This facilitates the easy insertion and location of the pole into the stand, without the need for the end of the pole to pass through the ballast material, and protects the end of the pole from possible harmful effects of the ballast material, as would be case if the pole was left unprotected mounted for long periods in a base container filled with water. which could rust a metal pole, or rot a wooden pole.

A major advantage of a stand of this type is that game components or other articles can be stored within the stand. In addition, the components of this stand can be "nested" into each other when stored or shipped in bulk and offer great space savings compared with the blow-moulded containers of the type which are frequently used as umbrella stands, but which have no detachable lid which would enable "pesting".

Another advantage of a stand with a removable lid is that it is easy to fill the container not only with ballast material such as water or sand. but with ballast made up from relatively large objects, such as rocks, stones or bricks, or water or sand-filled bottles.

EMBODIMENT OF THE INVENTION

An embodiment of the invention is described below with reference to the accompanying drawings which refer to the embodiment.

FIG. 1A: is a general arrangement drawing showing the stand in use on a hard surface during play of a tether tennis type game;
FIG. 1B: is a plan view of a stand according to the invention;
FIG. 1C: is an exploded side view of a cross section of the stand ;
FIG. 2: is a detailed cross sectional view of the stand showing the lid attached to the base. in the area of one of the four comer latches 32 shown in FIG. 1B, which comprise the secondary attachment system ;
FIG. 4: comprises four enlarged cross-sectional drawings 4A, B, C and D, showing different phases of the mating of an example of a tongue and flexible groove joint which comprises the primary attachment system, having a tongue which, at its apex, is larger than the open mouth of the groove, and where the axis of the tongue and groove are at an obtuse angle to the axis of the base.
FIG. 5: is a drawing of one type of latch 32 which may be used as part of the secondary locking system prior to application to the lid and base. together with the lid and base components to which it is about to be attached ;
FIG. 6: is a drawing of an example of a type of detachable clamp which, in association with the lid, may be used to clamp the pole into its mounted position.
FIGS. 8.1 to 8.7: illustrate various configurations of tongue and groove joints, some of which are suitable for a primary attachment system for this patent application.

With reference to the drawings :-

in FIG.1A a general arrangement drawing is shown of a stand according to this application, in use during play of a game of the tether tennis type, the stand being used on a hard surface ;
in FIG.1B a plan view is shown of a stand showing a detachable lid 12, the position of the four comer latches 32, which comprise the secondary attachment system, and the hole in the lid 15 for the pole;
FIG. 1C is an exploded cross-sectional view of the stand on the section A-A shown in FIG. 1B. This shows the base container 10 in the centre of the floor 11 of which is a socket 13 which is designed to receive and hold the bottom end of a pole 14. which is mounted in the stand. The lid 12 is shown above the base container 10 preparatory to fitting the lid 12. The lid has a thickened section 16 adjacent to the hole for the pole 15, so as to reinforce the lid in this area. At the periphery of the lid 12 is shown a groove 22, having an inner wall 24, and outer wall 26 (see FIG.2 for greater detail). The groove 22 is designed to fit closely over a tongue 20 at the periphery of the base container 10. Ballast material such as rocks or stones 50 are shown in place. Other ballast materials such as sand or water may alternatively be used.
FIG. 2 is an enlarged view of a cross section of a portion of the base 10 with the lid 12 attached to the base in the corner area of the stand shown in FIG. 1, showing a latch 32 which secures the lid 12 to the base 10. The latch 32 is one of the four latches shown in FIG.1B which constitute the secondary attachment system. The tongue 20 at the periphery of the base 10 is shown inserted, to the maximum extent, into the groove 22 at the periphery of the lid 12, and is enveloped and closely held by the inner surface of the groove which includes the inner wall 24, and the outer wall 26, of the groove 22.The latch 32 may be of many different forms and for example, a simple nut and bolt arrangement may be used, although in this embodiment a atch of the type shown in FIG.5 is preferred. In FIG.2 the latch 32 is not drawn to any specific design;
FIG. 4 comprises four drawings, 4A. B, C and D which are enlargements of a cross section of the stand at the zone of the joint between a lid and a base container which comprises the primary attachment system, having a typical tongue and flexible groove seal where the apex of the tongue is larger than the mouth of the groove. These figures show progressive stages in the attachment of the tongue and groove joint. FIG. 4A shows the lid 12 in position adjacent to the upper area of the wall of the base container 10, prior to attachment to the base 10. At the periphery of the base 10, a tongue 20 is shown which slopes outwardly at an obtuse angle 51, to the axis of the base container, the vertical line of which is indicated by line 50, shown in FIG. 4C, which mates with a complimentary flexible groove 22 at the periphery of the lid, such groove being defined by inner and outer walls 24 and 26 which, together with the apex (see FIG. 8.1) comprise the inner surface of the groove, and which also slopes at an obtuse angle to the axis of the base container.When the lid is presented to the base container with the object of attaching the lid to the base container, it will be seen that the groove in the lid will not freely slide down over the enlarged apex 27 of the tongue 20, which is larger than the opening of the groove 22 (see FIG.4B). The groove has to be initially pressed down over the enlarged apex 27 of the tongue 20.In this process the groove in the lid, being flexible, is forced open to accommodate the apex 27 of the tongue 20 (see FIG. 4C). The groove is then forced further down over the tongue. untii the tongue is inserted to the maximum extent into the groove. FIG. 4D shows the tongue and groove in this closed position. In this position the tongue is enveloped and held closely by the groove, and the configuration of the groove, which provides for the enlarged apex of the tongue, has allowed the groove to snap back substantially to its normal unstressed position by virtue of its natural flexibility and springiness.The enlarged apex of the tongue is comfortably accommodated within a corresponding cavity at the apex of the groove. This arrangement of tongue, fully inserted into a complimentary close fitting flexible groove, if correctly designed, gives an excellent watertight seal and resists sideways pressure from either side (as may be exerted in the plane of the lid by the pole during play of the tether tennis type games) as the tongue is held closely and supported on both sides by the walls of the groove.Conversely, should it be desired to remove the lid and detach the tongue from the groove, pressure has to be applied to pull the tongue free from the groove by forcing the groove to open, so as to release the tongue.In this configuration, the enlarged apex of the tongue, sitting inside the cavity at the apex of the groove, will tend to aid the positive restraint of the tongue within the groove, unless the groove is opened to enable the release of the tongue.
FIG. 5 shows a latch 32 of a type which may be used as an element of the secondary attachment system which positively attaches the lid to the base. This latch is preferably made of plastic and is similar in design to the quick release buckles used in back packs, camera cases and various types c f travel goods. The latch 32 has flexible arms 34A, 34B, which are free to bend towards each other when the latch is inserted down through the latch opening 40 in the lid 12, into the locking socket 33. which comprises part of the base 10. The arms 34A, 34B have outwardly pointing hooks 35 at the end of the arms 34A. 34B. When the latch has been inserted to its fullest extent into the locking socket 33, the hooks 35 emerge from the confines of the locking socket 33 at the lower end thereof, enabling the flexible arms 34A, 34B to spring outwards towards their natural position in the unstressed state, so that the upper faces of the hooks 35 are positioned underneath the bottom edge of the locking socket 33, thereby preventing the removal of the latch unless the ends of the tips of the flexible arms 34A. 34B are squeezed together so as to remove the upper faces of the hooks 35 from underneath the bottom edge of the locking socket 33.It will be appreciated that other (releasable) locking methods may be used as a secondary attachment means to securely and positively attach the lid to the base, such as hook and loop straps of the "VELCRO" (Trade Mark) type, or any other forms of releasable attachment, including clamps, catches, latches, twist locks, straps, ties, press-studs or snap fasteners, nut and bolt or screw arrangements, or the like.
FIG. 6 shows a section of the lid 12 fitted with an example of a type of removable clamp 30, which may be used to clamp the pole 14 into its mounted position. This clamp is used for applications requiring the positive locking of the pole into position. The lid 12 has been thickened at 16. so as to strengthen it in the area adjacent to the pole 14.
Various arrangements of tongue and groove joint are illustrated in drawings 8.1 to 8.7, not all of which, as is explained below. are appropriate for a stand as described in this patent application.
FIG 8.1 shows a cross sectional general arrangement of lid and base together with a close up view which illustrates the position 60 of the apexes of both the tongue and groove of the joint of the primary attachment system, when in the closed position.
FIG. 8.2 shows a groove as per the close up view in FIG. 8.1 illustrating a tongue inserted into a groove with the walls of both parallel to the axis 62 of the tongue and groove along the full length of the sides of the groove.
FIG. 8.3 shows a cross section of a groove with the tongue inserted in which the top section only of both the tongue and groove lie parallel to the axis of the tongue and groove. Below this section the wall of the groove does not abut the outer wall of the tongue and is at an angle inwardly towards the apex. Although this will tend to diminish the eifcctiveness of this seal, the extra length of the wall of the groove will tend to add to the strength of the seal even though it does not abut the outer wall of the tongue.
FIG. 8.4 shows a cross section of a groove and inserted tongue in which part of the outer wall of the tongue and the abutting face of the groove in this area diverge outwardly at angle xo from the parallel towards the apex in the area at the top of the apex, which tends to produce a very good seal.
FIG. 8.5 shows a groove and inserted hollow tongue with both outer walls of the tongue and abutting inner walls of the groove converging inwardly towards the apex at angle yo. This will tend to produce a weak seal.
FIG. 8.6 shows a wide short hollow tongue is shown enveloped by a groove. While this arrangement will provide a joint which is resistant to lateral shocks even though the tongue is relatively wide in relation to its depth, it will not provide a watertight joint.
FIG. 8.7 shows a shallow joint layout which will not provide a strong seal and watertight joint and cannot really be described as a tongue and groove joint.

Claims

A movable stand for vertical pole (14) support including a base container component (10) capable of holding ballast and a detachable lid component (12), said lid having a through-hole for a pole (14), and a socket (13) on the interior floor of said base container for receiving a bottom of a pole, the lid being attached to the base container characterised in that the lid and base are attached together by a two stage attachment system:

the primary attachment system consisting of a complemental inter-engageable tongue and groove formation (20,22) in which the tongue member (20) having a height greater than its width, is located around the complete periphery of one of said base container and said lid, where it fits into and is there enveloped and held closely along its entire length, by the groove (22) around the complete periphery of the other of said base container and said lid, such primary attachment system being capable of attachment and detachment by the application of finger pressure of no more than about 10 kilograms; and

a secondary attachment system consisting of two or more locking devices (32) at points around the periphery of the base container which lock the lid to the base container, and prevent the extraction of the tongue from the groove of the primary attachment stage, or the detachment of the lid from the base container, other than by the application of excessive force, having regard to the conventional use of the stand;

the locking devices of the secondary attachment system being also capable of attachment and detachment by the application of finger pressure of no more than about 10 kilograms.
The stand according to claim 1, characterised in that the primary attachment system is capable of attachment and detachment by the application of finger pressure of no more than about 3 kilograms and the secondary attachment system is capable of attachment and detachment by the application of finger pressure of no more than about 0.5 kilograms.
The stand, according to claim 1 characterised in that the primary attachment system includes a flexible groove (22) which is capable c f opening to accommodate the insertion of the tongue (20) when forced thereinto and is so configured that it is able to spring or snap back substantially to its normal configuration when not under stress, when the tongue has been inserted to the maximum extent into the groove, in which position the tongue is enveloped and held closely by the groove and is positively restrained in this position, unless sufficient force is exerted on the flexible groove so as to cause it to open to allow the release of the tongue.
The stand according to claim 3 characterised in that the tongue (20) and groove (22) are vertically non-aligned with respect to the base container (10).
The stand according to claim 1 characterised in that locking or clamping means (30) is provided so as to positively secure any pole which is mounted in the stand, so that the pole is unable to pull free from its mounted position in the stand, unless such locking or clamping means is released.